1. Field of the Invention
The present invention relates to a numerical control device, and more particularly to a numerical control device which enables easy and safe approach to a restarting machining point when restarting the machining for an operator.
2. Description of the Related Art
In a machining tool controlled by a numerical control device, machining needed to be restarted at an interrupting block or an easily-restartable block before the interrupting block, when the tool is broken or the machining which is interrupted before a holiday is restarted after a holiday. In this case, it is necessary that the tool is moved (approached) from the current position to the target restarting block position. International Publication No. WO03/032097A1 discloses a related art to enhance convenience of the operator at the approaching.
In the related art described in the International Publication No. WO03/032097A1, in the case that the operator performs manual operation approach with a handle etc. and at least one of the corresponding axes does not move back to the restarting machining point, the corresponding axis is positioned directly by a movement command to the restarting machining point (automatic operation approach). Since a procedure opposite to the above mentioned procedure is not assumed, it is necessary to perform the restarting operation from the beginning again, for performing the manual operation approach again during the automatic operation approach.
Practically, manual intervention is assumed to take place for avoiding interference of a workpiece or a machinery member with the tool during the automatic operation approach, or the like. In this case, it is necessary to reset the machining tool and restart the operation in the technique described in the International Publication No. WO03/032097A1. There is a problem (hereinafter referred to as “Problem 1”) that, since it is necessary, for the restart of the operation from the beginning, to select the restarting block, restore the modal data, and restart the restarting mode again, it takes time for the restarting and makes the operation by the operator complicated, for a large-scale program or the like.
In addition, there is a problem (hereinafter referred to as “Problem 2”) in the International Publication No. WO03/032097A1 that, visual checking and manual operation by the operator is needed for restarting machining of a complicated workpiece in the technique described, since it is not considered to avoid interference of the tool with the workpiece during automatic operation approach, thought there is a possibility that the workpiece and the tool intervene with each other during the approach when machining of the workpiece with complicated configuration such as an impeller is restarted at the machining block.
Furthermore, there is a problem (hereinafter referred to as “Problem 3”) in the International Publication No. WO03/032097A1 that, the numerical control device is not configured to output warning to the operator even when the direct movement of the tool from the current position by the automatic operation approach will cause interference, since the numerical control device does not check detailed positional relation such as distance between the restarting machining point and the current position when the automatic operation approach starts.